Acanthurus chronixis is a close relative of Acanthurus pyroferus, sharing the count of VIII dorsal spines and the same morphology, in particular the protruding snout (Randall 2001a). Its taxonomic status is uncertain due to limited number of specimens. There is taxonomic work underway to determine the status of this species. We accept current taxonomy that this species is valid (Eschmeyer 2011, J.E. Randall pers comm. 2011).

Justification:Acanthurus chronixis is known from a limited number of specimens: the holotype and two possible juveniles from Kapingamarangi Atoll, Caroline Islands and an individual collected in 1980. The estimated area of occupancy is 31 km² using 25 m depth layer analysis on ArcGIS, however, this species has only been collected in depths no greater than 6 m, so the AOO is much less than 31 km².There is taxonomic work under way to verify the taxonomic standing of this species, as it is involved in species complexes that mimic colour patterns. There is very little information available on the population status or life history characteristics of this species. Kapingamarangi Atoll is a highly isolated but heavily populated island. Local waters are presumably heavily fished with spearfishing occurring widely around the island (G. Edgar pers. comm. 2011). This species is therefore listed as Vulnerable under D2. We recommend continued research on this species' taxonomic standing, distribution, life history characteristics and population status. We accept current taxonomy that this species is valid (Eschmeyer 2011, J.E. Randall pers. comm. 2011) and although taxonomic problems persist for this putative species, it is clear that even at the population level, the only location where it occurs is subject to intensive harvesting.

Acanthurus chronixis is known only from Kapingamarangi Atoll, Caroline Islands. It is reported from southwestern Taiwan and southern Japan, however, reports from other areas are probably misidentifications of the juvenile stages of Acanthurus pyroferus (Randall 2002b, R.F. Myers pers. comm. 2011). The estimated area of occupancy (AOO) is 64 km² using coral layer analysis with the World Conservation Monitoring Centre's 1 km grid polygon.

There is very limited population information available for this species and this is attributed to its isolated range of distribution. This species was originally only known from the type specimens, however, an individual has been collected since its description in 1960 (accessed through the Fishnet 2 Portal, www.fishnet2.org, 2012-06-11).

Acanthurus chronixis was described from a single adult specimen collected over coral and sand bottom in less than 6 m (Randall 1960, 2001a). The sexes are separate among the acanthurids and there is no evidence of sexual dimorphism (Reeson 1983).

Surgeonfishes show varying degrees of habitat preference and utilization of coral reef habitats, with some species spending the majority of their life stages on coral reef while others primarily utilize seagrass beds, mangroves, algal beds, and /or rocky reefs. The majority of surgeonfishes are exclusively found on coral reef habitat, and of these, approximately 80% are experiencing a greater than 30% loss of coral reef area and degradation of coral reef habitat quality across their distributions. However, more research is needed to understand the long-term effects of coral reef habitat loss and degradation on these species' populations. Widespread coral reef loss and declining habitat conditions are particularly worrying for species that recruit into areas with live coral cover especially as studies have shown that protection of pristine habitats facilitate the persistence of adult populations in species that have spatially separated adult and juvenile habitats (Comeros-Raynal et al. 2012).